Blown Castor oil

Blown Castor oil is also known as oxidized Castor oil. 
Blown oil (in general) consist of triglyceride molecules with oxygen linkages to form oxidized polymers. 
They are manufactured under temperature/pressure controlled conditions in the presence of air. Oxidative and crosslink polymerization will take place at the double bonds and hydroxyl groups.
This will result in increased viscosity, specific gravity and reactivity.
The higher the viscosity, the higher the specific gravity, the acid value and the saponification value and the lower the iodine value and the hydroxyl value.